Consistent with the Biobehavioral Development objective of the NICHD strategic plan, we propose linking neural developmental trajectories in infancy with cognitive and neural function in middle childhood. Decades of work on sensitive periods from animal models predicts that early neurodevelopmental trajectories contribute to later behavior, cognitive, and neural function. Collectively, this research indicates that the brain is particularly sensitive to environmental inputs during early development, fundamentally altering developmental trajectories and later capacity. However, almost no studies in humans have explicitly examined the link between infant brain development and subsequent neural function and behavior, thus, it remains unclear what aspects of structural or functional development reflect these early periods of environmental sensitivity in the developing human brain. Attaining such information is a public health imperative, given that prevention efforts in early childhood rely on sensitive period theorizing. Information about neural development can neither contribute to nor be impacted by these efforts without these initial steps. The proposed study capitalizes on and extends an existing longitudinal neuroimaging study with neuroimaging data sampled frequently in early childhood (approximately at 0, 3, 6, 9, 12, 18, 24, 36, and 48 months of age). Previously this dataset has been used to develop novel imaging analysis techniques required to measure neural structure in the infant brain. Other studies of infant brain development have acquired data in a less dense fashion (e.g., at 0, 1, and 2 years). This unusually dense sampling approach which will allow us to use sophisticated longitudinal modeling techniques to characterize the developmental trajectories of brain development (between 0 and 4 years). We will use these trajectories to predict individual differences in neural function and cognitive task performance in middle childhood. Because we are beginning with an existing dataset, this is an efficient, highly innovative, and cost-effective proposal. We will need to acquire only a single additional neuroimaging and cognitive testing session between 7 and 8 years of age to complete this research study. This proof-of-concept study will serve as pilot data for a future application aimed at identifying how early neural trajectories predict function in a larger and more diverse sample of longitudinally-followed infants (currently being collected as part of U01-MH110274). Critically, information from this study will also immediately improve knowledge about how early neurodevelopmental trajectories predict later cognitive and neural function.